Often, an organic light-emitting diode (OLED) device has a sandwich-like structure, which includes an organic material layer disposed between an anode and a cathode. The organic material layer often includes a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, etc. An OLED device is a type of electrical-injection device. After applying an operating voltage between the anode and the cathode, holes are injected from the anode into the organic material layer and electrons are injected from the cathode into the organic material layer. The carriers, i.e., holes and electrons, form hole-electron pairs in the organic material layer. The hole-electron pairs then recombine to emit light.
Recently, transparent display technology has applications in window displays, instruments, devices, and other related fields.